Tollmann's bolide hypothesis is a hypothesis presented by Austrian

palaeontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

Edith Kristan-Tollmann Edith Kristan-Tollmann nee Edith Kristan (born 14 April 1934 in Vienna; died 25 August 1995) was an Austrian geologist and paleontologist. A prolific scientist with an interest in micropalaeontology and especially the foraminifera of the Triassic ...

and geologist

Alexander Tollmann Dr. Alexander Tollmann (27 June 1928 – 8 August 2007) was an Austrian professor of geology. He was born in Vienna. He had been professor at the Geologischen Institut of the University of Vienna since 1969. He was a political activist working to ...

in 1994. The

hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...

postulates that one or several

bolide A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large crater-forming body, or to one that explodes in the atmosphere. It can be a ...

s (

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

s or

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...

s) struck the Earth around 7640 ± 200 years

BCe Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the or ...

, with a much smaller one approximately 3150 ± 200 BCE. The hypothesis tries to explain early

Holocene extinctions The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

and possibly legends of the Universal Deluge. The claimed evidence for the event includes

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostra ...

studies of

tektites Tektites (from grc, τηκτός , meaning 'molten') are gravel-sized bodies composed of black, green, brown or grey natural glass formed from terrestrial debris ejected during meteorite impacts. The term was coined by Austrian geologist Franz ...

,Glass, B.P., 1978, ''Australasian Microtektites and the Stratigraphic Age of the Australites'' Bulletin of the Geological Society of America. v. 89, no. 10, pp. 1455–1458.Izokh, E.P., 1988, ''Age-paradox and the Origin of Tektites'' in J. Konta, ed., 2nd international conference on natural glasses'' Abstracts – International Conference on Natural Glasses-Prague, Czechoslovakia, 1988. v. 2, pp. 379–384.Prasad, N.S. and P.S. Rao, 1990, ''Tektites Far and Wide''. Nature. v. 347, no. 6291, pp. 340.

dendrochronology Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...

, and

ice core An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ic ...

s (from Camp Century,

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

) containing

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

and

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

(indicating an energetic ocean strike) as well as

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...

s (caused by extreme heating of air).

Christopher Knight Christopher or Chris Knight may refer to: Film and television *Christopher Knight (actor) (born 1957), American actor * Christopher Knight (filmmaker), blogger and filmmaker * Chris Knight (''Neighbours''), fictional character in the soap opera '' ...

and

Robert Lomas Robert Lomas is a British writer, physicist and business studies academic. He writes primarily about the history of Freemasonry as well as the Neolithic period, ancient engineering, and archaeoastronomy. Career In engineering and business stu ...

in their book, ''

Uriel's Machine ''Uriel's Machine: The Prehistoric Technology That Survived the Flood'' is a bestselling book published in 1999 by Christopher Knight and Robert Lomas. The book's name is derived from a character of the same name in the '' Book of Enoch''. In ...

'', argue that the 7640 BCE evidence is consistent with the dates of formation of a number of extant salt flats and lakes in dry areas of North America and Asia. They argue that these lakes are the remains of multiple-kilometer-high waves that penetrated deeply into continents as the result of oceanic strikes that they proposed occurred. Research by Quaternary geologists, palynologists, and others has been unable to confirm the validity of the hypothesis and proposes more frequently occurring geological processes for some of the data used for the hypothesis. The dating of ice cores and Australasian tektites has shown long time span differences between the proposed impact times and the impact ejecta products.

Scientific evaluation

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

geologists,

paleoclimatologist Paleoclimatology (British spelling, palaeoclimatology) is the study of climates for which direct measurements were not taken. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important to ...

s, and planetary geologists specialising in

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...

and

impacts have rejected Tollmann's bolide hypothesis.Deutsch, A., C. Koeberl, J.D. Blum, B.M. French, B.P. Glass, R. Grieve, P. Horn, E.K. Jessberger, G. Kurat, W.U. Reimold, J. Smit, D. Stöffler, and S.R. Taylor, 1994, ''The impact-flood connection: Does it exist?'' Terra Nova. v. 6, pp. 644–650. They reject this hypothesis because: # The evidence offered to support the hypothesis can more readily be explained by more mundane and less dramatic geologic processes # Many of the events alleged to be associated with this impact occurred at the wrong time (i.e., many of the events occurred hundreds to thousands of years before or after the hypothesized impacts); and # There is a lack of any credible physical evidence for the cataclysmic environmental devastation and characteristic deposits that kilometre-high

tsunamis A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater expl ...

would have created had they actually occurred. Post-Glacial Sea Level

Evidence used by proponents of the Tollmann's bolide hypothesis to argue for catastrophic

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

extinctions have alternative explanations by more frequently occurring geological processes. The chemical composition and presence of

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcano, volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used t ...

with the specific acidity spikes in the

ice cores An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ic ...

shows evidence that they result from

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...

instead of impact origins.Hammer, C.U., H.B. Clausen, and W. Dansgaard, 1980, ''Greenland ice sheet evidence of post-glacial volcanism and its climatic impact''. Nature. v. 288, no. 5788, pp. 230–235.Zielinski, G.A., P.A. Mayewski, L.D. Meeker, S. Whitlow, and M.S. Twickler, 1996, ''A 110,000-year record of explosive volcanism from the GISP2 (Greenland) ice core''. Quaternary Research. v. 45, no. 2, pp. 109–118. Also, the largest acidity spikes found in

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

ice cores have been dated to 17,300 to 17,500 BP, which is significantly older than hypothetical Holocene impacts.Hammer, C.U., H.B. Clausen and C. Langway, Jr., 1997, ''50,000 years of recorded global volcanism''. Climatic Change. v. 35, no. 1, pp. 1–15. The formation of modern

salt lake A salt lake or saline lake is a landlocked body of water that has a concentration of salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of salt per litre). ...

s and salt flats is explained by the concentration of salts and other

evaporite An evaporite () is a water-soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocea ...

minerals by the

evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...

of water from stream-fed lakes lacking external outlets, called

endorheic An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes ...

lakes, which commonly occur in arid climates on both hemispheres on Earth. The composition of the salts and other evaporite minerals found in these lakes is consistent with their precipitation from dissolved material continually carried into the lakes by rivers and streams and subsequent concentration by evaporation, instead of evaporation of seawater.Eugster, H.P., 1980, ''Geochemistry of Evaporitic Lacustrine Deposits''. Annual Review of Earth and Planetary Sciences. v. 8, pp. 35–63.Spencer, R.J., Eugster, H.P., and Jones, B.F., 1985, ''Geochemistry of Great Salt Lake, Utah II: Pleistocene-Holocene evolution''. Geochimica et Cosmochimica Acta. v. 49, no. 3, pp. 739–747.Hart, W.F., J. Quade, D.B. Madsen, D.S. Kaufman, and C.G. Oviatt, 2004, ''The 87Sr/86Sr ratios of lacustrine carbonates and lake-level history of the Bonneville paleolake system''. Geological Society of America Bulletin. v. 116, no. 9–10, pp. 1107–1119. Whether a lake becomes salty or not depends on whether the lake lacks an outlet and the relative balance between the inflow and outflow of lake waters via evaporation. Ocean water accessing a continental lake as the result of a single catastrophic event, as Tollmann's hypothesis proposes, would contain an inadequate amount of dissolved minerals to produce, when evaporated, the vast quantities of salts and other evaporites found in the salt lakes, flats, and pans cited as evidence of a mega-

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...

by this hypothesis.

Geological criticism

Isostatic rebound

Many published papersPeltier, W.R. 1998, ''Global glacial isostatic adjustment and coastal tectonics'' in I. Stewart and C. Vita-Finzi, eds., pp. 1–29. Coastal Tectonics. Special Publication no. 146, pp. 1–29. Geological Society of London, London.Peltier, W.R., 2002, ''Global glacial isostatic adjustment: Palaeogeodetic and space-geodetic tests of the ICE-4G (VM2) model''. Journal of Quaternary Science. v. 17, no. 5–6, pp. 491–510. demonstrate that

isostatic depression Isostatic depression is the sinking of large parts of the Earth's crust into the asthenosphere caused by a heavy weight placed on the Earth's surface, often glacial ice during continental glaciation. Isostatic depression and isostatic rebound o ...

of the Earth's crust happened in the early Holocene. This process has led to submerging substantial portions of coastal areas adjacent to continental

ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at Las ...

s and resulted in the accumulations of marine

sediments Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand a ...

and

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s within them. A well-documented example of flooding caused by isostatic depression is the case of Charlotte, The Vermont Whale,Wright, W.A., 2000
''Charlotte, The Vermont Whale An Electronic Museum.''
niversity of Vermont, Burlington, Vermont a fossil whale found in the deposits of the former

Champlain Sea The Champlain Sea (french: Mer de Champlain) was a prehistoric inlet of the Atlantic Ocean into the North American continent, created by the retreating ice sheets during the closure of the last glacial period. The inlet once included lands in ...

. Like many similar marine deposits, the sediments, which accumulated within the Champlain Sea lack the physical characteristics; i.e. sedimentary structures, interlayers, and textures, that characterise sediments deposited by a mega-

. These deposits and the associated fossils have been dated to significantly earlier periods than the times the bolide hypothesis proposed. In the case of the Champlain Sea, its sediments started to accumulate around 13,000 BP, almost 3,400 years before the oldest of the hypothesized Holocene bolide impacts.

Dating

A significant amount of the physical evidence used by Kristan-Tollmann and Tollmann, as supporting their hypothesis, is either too old or too young to have been created by this hypothesized impact. In many cases, it is hundreds to thousands, and in one case hundreds of thousands, of years too old to be credible evidence of a Holocene impact. The research that dates the

tektite Tektites (from grc, τηκτός , meaning 'molten') are gravel-sized bodies composed of black, green, brown or grey natural glass formed from terrestrial debris ejected during meteorite impacts. The term was coined by Austrian geologist Franz ...

s, which Tollmann's bolide hypothesis regards as indicative for the timing of the impact, is outdated. Later research,Schneider, D.A., D.V. Kent, G.A. Mello, 1992, ''A detailed chronology of the Australasian impact event, the Brunhes–Matuyama geomagnetic polarity reversal, and global climatic change''. Earth and Planetary Science Letters. v. 111, no. 2–4, pp. 395–405.Shoemaker E.M., and H.R. Uhlherr, 1999, ''Stratigraphic relations of australites in the Port Campbell Embayment, Victoria''. Meteoritics & Planetary Science. v. 34, no. 3, pp. 369–384.Lee, M.-Y., and K.-Y. Wei, 2000, ''Australasian microtektites in the South China Sea and the West Philippine Sea: Implications for age, size, and location of the impact crater''. Meteoritics & Planetary Science. v. 35, pp. 1151–1155. has dated the Australasian tektites to the

Middle Pleistocene The Chibanian, widely known by its previous designation of Middle Pleistocene, is an age in the international geologic timescale or a stage in chronostratigraphy, being a division of the Pleistocene Epoch within the ongoing Quaternary Period. The ...

; about 790,000 years BP. In addition, the formation of salt lakes and salt flats is neither synchronous nor consistent with the hypothesized impacts having occurred about either 9,640 BP or 5,150 BP. For example, in the case of

Lake Bonneville Lake Bonneville was the largest Late Pleistocene paleolake in the Great Basin of western North America. It was a pluvial lake that formed in response to an increase in precipitation and a decrease in evaporation as a result of cooler temperature ...

Lake Lahontan Lake Lahontan was a large endorheic Pleistocene lake of modern northwestern Nevada that extended into northeastern California and southern Oregon. The area of the former lake is a large portion of the Great Basin that borders the Sacramento Rive ...

Mono Lake Mono Lake ( ) is a saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes high levels of salts to accumulate in the lake which make its water alk ...

, and other

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

pluvial lake A pluvial lake is a body of water that accumulated in a basin because of a greater moisture availability resulting from changes in temperature and/or precipitation. These intervals of greater moisture availability are not always contemporaneous ...

s in the western United States, the transition to salt lakes and salt flats occurred at different times between 12,000 and 16,000 BP.Benson, L., 2004, ''Western lakes'', in Gillespie, A.R., Porter, S.C., and Atwater, B., eds., pp. 185–204. The Quaternary Period in the United States – Developments in Quaternary Science. Amsterdam: Elsevier. Thus, the change from freshwater to salty water and eventually salt flats started over 2,400 to 6,400 years before the oldest of the impacts hypothesized by the Tollmann bolide hypothesis occurred. As a result, it is impossible that the formation of these salt lakes could have been associated with the impact hypothesized by Kristan-Tollmann and Tollmann.

Megatsunami

There exists a lack of credible physical evidence of either multiple-kilometer-high

waves penetrating deeply into continents, and the ecological devastation these would have caused. Thousands of paleoenvironmental records constructed from the study of lakes, bogs, mires, and river valleys all over the world by

palynologists Palynology is the "study of dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and '' -logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposit ...

have not shown the existence of such a

megatsunami A megatsunami is a very large wave created by a large, sudden displacement of material into a body of water. Megatsunamis have quite different features from ordinary tsunamis. Ordinary tsunamis are caused by underwater tectonic activity (movemen ...

. In the case of North America, research published by various authorsBryant, V.M., Jr., and R.G. Holloway, 1985, ''Pollen Records of Late-Quaternary North American Sediments''. Dallas, American Association of Stratigraphic Palynologists. Jacobson, G.L., Jr., T. Webb, III, and E.E. Grimm, 1987, ''Patterns and rates of vegetational change during the deglaciation of North America''. in W. F. Ruddiman and H. E. Wright, Jr., eds., pp. 277–287. North America Adjacent Oceans During the Last Deglaciation. The Geology of North America. K-3. Geological Society of America, Boulder, Colorado.Shuman, B., P. Bartlein, N. Logar, P. Newby, T. Webb, III, 2002, ''Parallel climate and vegetation responses to the early Holocene collapse of the Laurentide Ice Sheet''. Quaternary Science Reviews. v. 21, no. 16–17, pp. 1793–805.Grimm, E.C. and G.L. Jacobson, Jr., 2004, ''Late Quaternary vegetation history of the eastern United States''. in Gillespie, A.R., S.C. Porter, and B.F. Atwater, eds., pp. 381–402. The Quaternary Period in the United States – Developments in Quaternary Science, Amsterdam, Elsevier. provides detailed records of paleoenvironmental changes that have occurred throughout the last 10,000 to 15,000 years as reconstructed from

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...

and other paleoenvironmental data from over a thousand sites throughout North America. These records do not recognise indications of either a resulting catastrophic environmental devastation or layers of

tsunami deposit A tsunami deposit (the term tsunamiite is also sometimes used) is a sedimentary unit deposited as the result of a tsunami. Such deposits may be left onshore during the inundation phase or offshore during the 'backwash' phase. Such deposits are us ...

s, which the mega-tsunamis postulated by Tollmann's bolide hypothesis would have created. Paleovegetation mapsOverpeck, J.T., R.S. Webb, and T. Webb., 1992. ''Mapping eastern North American vegetation change over the past 18,000 years: no-analogs and the future''. Geology. v. 20, no. 12, pp. 1071–1074. illustrate a distinct lack of the dramatic changes in North American paleovegetation during the Holocene, which would be expected from the cataclysmic ecological and physical destruction that a continental-wide mega-tsunamis would have certainly have caused. Grimm et al. in a paper published in ''

Science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence for ...

'' in 1993,Grimm, E.C., G.L. Jacobson Jr., W.A. Watts, B.C.S. Hansen, and K.A. Maasch, 1993, ''A 50,000-Year Record of Climate Oscillations from Florida and Its Temporal Correlation with the Heinrich Events.'' Science. v. 261, no. 5118, pp. 198–200. documented a 50,000-year-long record of environmental change by the analysis of pollen from an core from

Lake Tulane Lake Tulane in Florida is one of numerous natural lakes that occupy sinkholes, which were formed by the dissolution of Eocene limestone at depth. Lake Wales Ridge, within which Tulane Lake lies, is a linear highland that consists of unconsolidated ...

in Highland county, Florida. Because of the low-lying nature of the peninsula, in which this part of Florida lies, this lake and the area around it would have been flooded and covered by tsunami deposits along with many of the other lakes and bogs described in their, and other publications. The forests and associated ecosystems of these areas would have been flooded and completely destroyed by the mega-tsunamis proposed by Kristan-Tollmann and Tollmann. Despite its location, both the core and the pollen record recovered from Lake Tulane lacks any indication of an abrupt, catastrophic environmental disruption, which the mega-tsunamis proposed by Tollmann's bolide hypothesis would have caused. Sedimentary cores obtained from Florida and other locations also lack sedimentary layers that have the characteristics of sediments deposited by either tsunamis or mega-tsunamis. The cataclysmic scale of physical and ecological destruction that a megatsunami, like the one proposed by Kristan-Tollmann and Tollmann, would have caused, has not been recognised within the majority of long-term environmental records. Over a thousand cores from North America for which Holocene paleoclimatic and paleoenvironmental records have been reconstructed do not show evidence for the drastic environmental changes resulting from a large Holocene impact. There is a similar lack of evidence for mega-tsunami-related, Holocene, catastrophic environmental disruptions, and deposits reported from environmental records reconstructed from thousands of locations from all over the world. Other megatsunamis have been shown in coastal sediments analysed by geologists and palynologists and point to tsunamis locally caused by either earthquake,

volcanic eruption Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...

s, or submarine slides. These non-impact related tsunamis show abundant records of their environmental effects through the study of pollen from cores and exposures. Members of the Holocene Impact Working Group have published papers advocating the occurrence of mega-tsunamis created by extraterrestrial impacts at various times during the Holocene and Late Pleistocene.Blakeslee, S., 2006
''Ancient Crash, Epic Wave.''
New York Times, 14 November 2006. However, none of these proposed impacts match either the cataclysmic scale or timing proposed by Kristan-Tollmann and Tollmann for their hypothesized bolide.

References

External links

* Pinter, N., and S.E. Ishman, 2008
''Impacts, mega-tsunami, and other extraordinary claims'' PDF version, 304 KB
GSA Today. vol. 18, no. 1, pp. 37–38. {{DEFAULTSORT:Tollmanns bolide hypothesis Historical geology Hypothetical impact events Extinction events